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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 27 September 2017 by dana1981

Last week, Nature Geoscience published a study suggesting that we have a bigger remaining carbon budget than previously thought to keep global warming below the 1.5°C aggressive Paris climate target. Many scientists quickly commented that the paper’s conclusion was based on some questionable assumptions, and this single study shouldn’t be blindly accepted as gospel truth.

Conservative media outlets did even worse than that. They took one part of the paper’s analysis out of context and grossly distorted its conclusions to advance their anti-climate agenda.

1.5°C might indeed be a geophysical impossibility

The study used the UK Met Office and Hadley Centre’s HadCRUT4 global temperature data set to conclude that so far we’ve warmed 0.93°C from the mid-1800s to 2015, compared to the Paris target of 1.5°C above pre-industrial temperatures. Several climate scientists immediately noted a problem here – HadCRUT4 excludes the Arctic region, which is the fastest-warming part of the planet. Hence it’s one of the least globally-representative temperature datasets. According to more globally-complete data sets like Berkeley Earth, the warming we’ve seen is closer to 1.1°C.

A third problem discussed by climate scientists Stefan Rahmstorf at RealClimatei nvolves the way the study authors defined the budget itself. They looked at how much carbon will be emitted at the time we reach 1.5°C warming, but because of what’s known as the ‘thermal inertia’ of the oceans, and because sunlight-reflecting pollutants will fall out of the atmosphere as we shift away from dirty coal power, the planet will keep warming after that time.

But ultimately that’s a relatively unimportant point. Even if limiting global warming to 1.5°C is still technically feasible, it will take immense global action to achieve it. If it’s infeasible, we still need immense global action to try and stay below 2°C, or 2.5°C, or to slow global warming as much as possible to avoid catastrophic consequences.

From a real-world policy perspective, we need all hands on deck whether the conclusions of this paper are right or wrong.

Biased right-wing media turns on the spin cycle

Of course, many conservatives who want to maintain the status quo object to that reality. As we saw with the recent Ipso ruling, many right-wing media outlets will jump at any opportunity to misrepresent climate research in order to advance the climate denial agenda.

I think some press reporting is misleading as our paper did not assess climate impacts or climate model performance. Rather, our paper confirms the need for much increased urgent action from around the world if society stands a chance of limiting warming to 1.5C.

Myles Allen and study lead author Richard Millar took to The Guardian to criticize the conservative media outlets that had misrepresented their research. I spoke to Allen, who clarified that he was trying to explain that temperatures didn’t seem to be responding to carbon emissions as fast as the models used in the last IPCC report anticipated. Except the reasons for that have already been identified - the actual global energy imbalance hasn’t been as large as in the scenarios input into the climate models, and we have to compare apples-to-apples temperatures. As Allen and Millar wrote in The Guardian:

the IPCC specifically assessed that temperatures in the 2020s would be 0.9-1.3C warmer than pre-industrial, the lower end of which is already looking conservative. Anyone who had troubled to read our paper would have found this “IPCC AR5 Ch11 projection” helpfully labelled on two of our figures, and clearly consistent with our new results.

It appears that Ben Webster didn’t understand Allen’s explanation, and Allen was perhaps a bit careless with some of his words. As a result, Webster quoted Allen saying the models were running too hot. Conservative ‘journalists’ and opinion writers saw that seemingly juicy quote and without speaking to Allen or any other climate scientists, ran with it, completely distorting the actual findings of the paper in the process.

It’s been clear for years that conservative media outlets thrive on any comments from climate scientists that can be construed as supporting climate denial myths (model reliability being among the most popular myths). It’s unfortunate that climate scientists have to be so careful about what they say, but that’s the reality we live in. Biased conservative media outlets aren’t interested in accurately reporting scientific findings; they’re interested in advancing the climate denial agenda of manufacturing doubt in order to erode public support for climate policies. And so the grossly misleading ‘alarmist scientists admit they were wrong’ story was echoed by Breitbart, the Daily Mail, the Sun, the Herald Sun, Fox News, the Daily Caller, and many more.

"the study authors... looked at how much carbon will be emitted at the time we reach 1.5°C warming" In what way is this a useful metric? It's like saying "if you burn this much diesel, your ship will get to Portsmouth harbor in one hour". And a minute later, it'll sail right past it on its own momentum ("...because of what’s known as the ‘thermal inertia’ of the oceans" - yup).

A few years ago, Dr Mann published some calculations that indicated that if the ECS is 3C, as expected, then at todays 405ppm of CO2 we'll essentially hit 2C by 2100 (this assumes coal aerosols rain out, a 0.5C hit). I find this a far more useful way of discussing how much wiggle room Earth has left before we exceed these targets.

The temperatures above 80N are really starting to trend... and business and industry need long lead times to react properly.

Resource bottlenecks have always been the predicted result when people start realising all at once what the truth is. Why is this truth being hidden from the consuming taxpayer who a) lives in a democracy and b) is supposed to have consumer rights?

We need to decide what is the most important information and each tell a thousand of our friends as fast as possible: I put it that this graph is one of those most important pieces of information...

Why is it that projecting out from the IPCC models gets you 70 GtC remaining whereas this new analysis gets you 200 GtC? From what I've read it seems like they haven't changed anything about the models but only adjusted them to todays temperature and emissions. You get 70 GtC if you project outward without adjustment, but the models have underestimated where we would be emissions-wise and slightly overestimated where we would be temperature-wise. So if you project outward from 545 GtC you're projecting out from the 2020's where the median of the models predicted we would be for emissions, which is also at a higher temperature and atmospheric co2 concentration. Is all of that right?

I understand that the actual difference between the models and observations is not 0.3 C but is much smaller. I'm just wondering how you get 3x more carbon budget while still projecting the same rates of warming and without a new "warming per tonne of co2 emitted". Is it simply the small adjustemnt to account for todays temperature and emissions that gets you that?

It's a combination of things. Firstly theres very little discrepency between models and latest real world temperatures taken as a average of all temperature data sets. But the study uses the hadcrut data which shows the least warming ( I have no idea why they would do that and select just one set of data as opposed to an average) so magnifies the discrepency. Secondly theres some issue about how the study considers carbon budgets explained in the article. But be warned its a bit headache inducing!